I am trying to to set a global screensaver and blanking idle timout (with screen locking) that will affect all new user accounts. I noticed that gnome-screensaver in 12.04 when configured by a user, writes some data to a blob in ~/.dconf, but I have no idea how to set it globally. I also know that the global timeout is 10 minutes with blanking, but have no idea where this is set system wide. I find the whole dconf transition a bit difficult.

If it is not possible to configure gnome-screensaver this way, I would be quite interested in a solution with xscreensaver/xlock.

The purpose of this is to set a blank screen with automatic locking. Both because of resource usage and security.

Forgot to mention that this is a default Ubuntu 12.04 desktop install with Unity and LightDM. I will however install gnome-shell and gnome-session-fallback to let people choose. It would be nice if a solution works across different sessions.

xscreensaver option (tested on Xubuntu 12.04): Edit /etc/X11/app-defaults/XScreenSaver (as root) to set lock to True and lockTimeout to whatever time you want. This will change the default for all users, but the users can still change it using the normal preference mechanism.